A new natural mycotoxin was isolated from the fermentation broth of Trichoderma sp. Jing-8 and the structure was determined as alternariol 1'-hydroxy-9-methyl ether (1), together with twelve known compounds. The structures were elucidated on the basis of their 1D, 2D NMR spectra and mass spectrometric data. Compounds 1, 8 and 9 indicated inhibitions against germination of the seeds of cabbage with MICs < 3 μg/mL. The compound 1 showed the antibacterial activity against Bacillus subtilis and Staphylococcus aureus with MICs at 64 μg/mL. Compound 1 and 3 showed significant DPPH radical-scavenging activities with IC at 12 μg/mL, respectively. The OH at C-1' in compound 1 decreased the cytotoxicity of these mycotoxins. A primary structure-activity relationship about the alternariol derivatives was discussed. Compounds 2-7 and 8 were the first time to be isolated from the Trichoderma.

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Two new cyclic tetrapeptides, cyclo(l‐Val‐l‐Leu‐l‐Val‐l‐Ile) (1) and cyclo(l‐Leu‐l‐Leu‐l‐Ala‐l‐Ala) (2), and 15 known compounds, cyclo(Gly‐l‐Leu‐Gly‐l‐Leu) (3), cyclo(l‐Ser‐l‐Phe) (4), cyclo(l‐Leu‐l‐Ile) (5), cyclo(l‐Tyr‐l‐Phe) (6), cyclo(Gly‐l‐Trp) (7), cyclo(l‐Leu‐l‐Tyr) (8), cyclo(Gly‐l‐Phe) (9), cyclo(l‐Phe‐trans‐4‐hydroxy‐l‐Pro) (10), cyclo(l‐Leu‐l‐Leu) (11), cyclo(l‐Val‐l‐Phe) (12), cyclo(l‐Val‐l‐Leu) (13), cyclo(l‐Ile‐l‐Ile) (14), cyclo(l‐Tyr‐l‐Tyr) (15), turnagainolide A (16), and bacimethrin (17) were isolated from the fermentation broth of Streptomyces rutgersensis T009 obtained from Elaphodus davidianus excrement. Their structures were identified on the basis of spectroscopic analysis. Meanwhile, the absolute configurations of the amino acid residues of compounds 1 and 2 were determined by advanced Marfey method. Compound 3 was obtained from a natural source for the first time. The X‐ray single crystal diffraction data of bacimethrin (17) were also reported for the first time. Compounds 1 – 17 exhibited no antimicrobial activities with the MICs > 100 μg/ml.

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